Throttle breakover devices are known for limiting the force exerted upon an engine throttle lever by a throttle cable or linkage. The throttle cable exerts the force on the throttle lever in response to the depression of an accelerator pedal through a stroke. Typically, after the lever has been moved by the cable to a maximum (full throttle) position, the accelerator pedal may still be depressed through a remaining "breakover" portion of the stroke. If the accelerator pedal and the throttle lever are unyieldingly interconnected by the cable, damage to the throttle could result from the accelerator pedal being forced through the remaining "breakover" portion of the stroke.
Because it is impractical to provide an accelerator pedal stroke which "bottoms-out" simultaneously with the throttle lever reaching the full throttle position, throttle devices are needed to limit the forces generated in the connection between the cable and the throttle lever. Typically, throttle breakover devices have a cable (or rod) with one end coupled to an accelerator pedal and the other end slidably coupled to the throttle. Often, an idle spring is provided which biases the throttle towards an idle position. In response to the accelerator pedal moving through the stroke, the cable pulls the throttle lever, against the idle spring bias, from the idle position to a maximum position. Once the full throttle position is reached, a throttle breakover device at the coupling of the throttle lever operates to absorb the breakover movement of the cable, thereby limiting the force of the cable on the throttle lever.
U.S. Pat. No. 2,312,274 to Stortz discloses one throttle breakover device. The Stortz device discloses a throttle cable supported upon an arcuate rim mounted on a throttle arm. The cable has a threaded extension which is slidably attached through a flange protruding above the distal end of the arcuate rim. A coil spring surrounds the threaded extension extending beyond the flange. The spring is held in place by an end nut threaded onto the threaded extension atop the spring, and a flange nut threaded onto the extension abutting the flange, thereby compressing the spring between the end nut and the arcuate rim flange. In this way, as the cable supported upon the arcuate rim is pulled, the rim rotates the throttle arm to the maximum position. Thereafter, the cable "breakover" movement is absorbed by the spring.
Because motor vehicle accelerator pedals are repeatedly depressed, the Stortz cable is repeatedly bent along the arcuate rim. Such repetitive bending can lead to the fatigue stress fracture of the cable. Moreover, if the cable is torsionally twisted during installation, these stresses may also contribute to cable fatigue. Another drawback of the Stortz device is the possibility that the end and flange nuts may become loosened over time due to the engine vibration. If the end nut were to detach from the extension, the cable would slip from the arcuate rim, resulting in the inability to accelerate the engine. Finally, the coil spring of the Stortz device may be subject to buckling if the spring is lengthened to accommodate a long breakover stroke.
Another example of a breakover device includes a throttle lever with independent base and upper portions which are coupled by a coil spring. After a cable pulls the lever into the full throttle position, the spring flexes to allow the upper lever portion to pivot through a breakover angle, thereby absorbing the additional movement of the cable. This device requires a lever indexing procedure for proper breakover operation.
A need exists for an improved throttle breakover apparatus that overcomes these and other disadvantages of the prior art.